Fear not, this is not a post about colonoscopies. Here’s how to think about the colon as a punctuation mark: (<—-that’s a colon)

Colons are like the blare of a trumpet (they say, “Ta dah! Here it comes!”). You’ve just written a sentence and you need to expand on it. The original sentence gives you a promise, and what follows the colon is used for three reasons:

to give an example We needed only one more thing for our party: a good DJ.

to introduce a quotation My sister’s words were uplifting: “Your haircut is so good, you could be in a shampoo ad.”

to introduce a list At Trader Joe’s I bought two essential items for dinner: cheese and wine.

I often hear people talk about a phenomenon, which refers to one thing or situation, when they need the plural of phenomenon—which is phenomena, referring to more than one thing or situation.

• Global warming is a potentially disastrous phenomenon.

• The phenomena that contribute to global warming are being studied extensively in hopes of avoiding worldwide catastrophes.

Another pair often misused are criteria (plural) and criterion (singular). If you have only one standard that must be met, you want criterion.

But here’s one you can stop worrying about: datum. That’s the singular of data. Today, data is used for both singular and plural. Why? Because common usage changes all languages. However, if you are using data as a plural, make your verb plural also:

• The scientific data are unequivocal that ocean temperatures are rising rapidly.

Speaking of locutions that make me cringe (we were, weren’t we?), the suffix “—wise” is near the top of my list. Limit it to a very few situations:

• Clockwise, counter clockwise

• Otherwise

• Lengthwise

Spare others from uses such as “healthwise,” “timewise,” “costumewise,” “stylewise.”

Instead of saying or writing, “Healthwise, I’ve had some problems with my elbow recently,” just drop that silly introductory word. It adds nothing. Nor does “costumewise”: “Costumewise, I’m going as Darth Vader as a schoolboy.” Just describe the getup you are planning on wearing to that Star Wars-themed Halloween party.